Twilio Review 2025: What Building Real Notification Systems Taught Me

The Time I Spent $400 in One Night on Accident

Let me tell you about the most expensive bug I have ever written. It was a Tuesday night, and I was building an appointment reminder system for a healthcare client. Simple concept: send an SMS to patients 24 hours before their appointment. I wrote the Twilio integration in about thirty minutes. The code worked. The tests passed. I deployed it to staging and sent a few test messages to my own phone. Everything looked great.

What I forgot to do was add a check for whether a reminder had already been sent. The cron job ran every five minutes. Every five minutes, it queried all appointments within the next 24 hours and sent an SMS for each one. By the time I checked my staging logs the next morning, the system had sent 47,000 SMS messages to about 3,200 phone numbers. Twilio charged $0.0079 per message. The bill was $371.30, plus phone number rental. On a staging environment. With test data that happened to have real phone numbers in it.

I called Twilio support. They were sympathetic but firm: the messages were sent, the charges were valid, and they could not reverse them. Fair enough. That was my fault, not theirs. But that experience taught me something every Twilio developer learns eventually: pay-as-you-go pricing is a feature and a trap. It removes barriers to getting started and creates a very expensive ceiling if you are not careful. I now have spending alerts set at $10, $50, and $100. Every Twilio project I build has rate limiting and deduplication before a single API call is made. Learn from my mistake.

Why Every Developer Ends Up at Twilio Eventually

I have tried to use alternatives. Genuinely tried. Vonage is cheaper per message. Amazon SNS is dirt cheap if you are already on AWS. MessageBird (now Bird) has a nice visual workflow builder. And every time, I end up back on Twilio. The reason is boring but real: the developer experience is just better.

Sending your first SMS with Twilio takes about eight minutes from account creation to receiving the message on your phone. I know because I timed it for this review with a fresh account. Create account, verify phone number, get trial credit, install the Python SDK (pip install twilio), write five lines of code, run the script, message arrives. The documentation walks you through it step by step with copy-pasteable code in six languages. The error messages tell you what went wrong in plain English. The console shows you every message with delivery status, timestamps, and pricing.

Compare that with Amazon SNS, where I spent forty minutes the first time just figuring out the IAM permissions needed to send a single SMS. Or Vonage, where the documentation is decent but the SDK naming conventions are inconsistent and the console feels like it was built in 2015. Twilio's developer experience is not just good by telecom standards. It is good by any standard. Their docs are better than most SaaS companies' entire products.

The SMS Reality Check: 10DLC and Deliverability

If you are building any SMS feature for US phone numbers in 2025, you need to understand 10DLC. This is not optional. This is not a nice-to-have. If you skip this section, you will discover it the hard way when your messages stop delivering.

10DLC stands for 10-Digit Long Code, and it refers to the registration system that US carriers now require for application-to-person (A2P) messaging sent from standard phone numbers. Before 10DLC, you could buy a Twilio phone number and start sending SMS immediately with decent deliverability. Those days are over. Carriers like T-Mobile, AT&T, and Verizon now filter unregistered traffic heavily. If you send more than a handful of messages per day from an unregistered number, your deliverability will tank -- messages will silently fail or get marked as spam.

The registration process through Twilio involves creating a Brand (your company identity), creating a Campaign (the specific use case for your messaging), and waiting for carrier approval. The approval process takes anywhere from three days to three weeks depending on the campaign type and carrier. The vetting fees are $4 for standard vetting or $40 for secondary vetting if standard fails. Once approved, your throughput and deliverability improve dramatically, but the process itself is bureaucratic and frustrating.

Twilio handles the 10DLC submission process as well as anyone, but it is worth acknowledging that this is a regulatory burden, not a Twilio feature. Every CPaaS provider deals with the same requirements. Twilio's advantage is better documentation of the process and more responsive support when registrations get stuck in review.

Voice API: More Powerful Than You Think

Most people think of Twilio as an SMS company. That undersells the voice API by a lot. I built a customer support phone tree for a client last year -- the kind where you call, hear "Press 1 for billing, press 2 for support," and get routed to the right team. With Twilio, the entire thing was about 200 lines of Python and some TwiML XML. It handled call routing, hold music, voicemail, call recording, and transcription.

TwiML is the XML markup language that controls call flow, and it is one of those things that sounds terrible in concept (XML for phone calls?) but works brilliantly in practice. You return TwiML from your webhook endpoints, and Twilio executes it in sequence. <Say> speaks text to the caller. <Gather> collects keypad input. <Dial> connects to another number. <Record> records audio. You can build surprisingly sophisticated phone systems by composing these building blocks.

The voice intelligence features that Twilio added recently are genuinely useful. Automatic speech recognition can transcribe calls in real-time. Sentiment analysis flags calls where customers are getting frustrated. Call summarization generates a brief recap of what was discussed. If you are processing hundreds of support calls per day, this is not a gimmick -- it saves hours of manual review time.

Voice pricing is $0.014 per minute for outbound calls to US numbers and $0.0085 per minute for inbound. Those numbers seem tiny until you scale. A support line handling 500 inbound calls per day at an average of 6 minutes each runs about $765 per month in call charges alone, plus phone number rental and any recording or transcription costs. Manageable, but not trivial.

SendGrid: The Email Side of the House

Twilio acquired SendGrid in 2019, and it has become the default email delivery platform for a large chunk of the developer world. I use it for transactional emails -- account verification, password resets, order confirmations, that sort of thing. The Email API is clean, the deliverability is excellent (my inbox placement rate is consistently above 98%), and the event webhooks give me visibility into opens, clicks, bounces, and spam complaints.

Where SendGrid gets interesting is the scale. A side project of mine sends about 5,000 transactional emails per month and fits comfortably within SendGrid's free tier (100 emails per day). A client's e-commerce platform sends 2 million emails per month on the Pro plan at $89.95/month. The same platform handles both volumes without breaking a sweat.

The marketing email features are fine but not why you choose SendGrid. If your primary need is marketing email campaigns with sophisticated automation, Mailchimp, Klaviyo, or ConvertKit are better tools for that specific job. SendGrid's sweet spot is transactional email delivery where reliability and deliverability matter more than pretty drag-and-drop editors.

The Bills: Real Numbers from Real Projects

Let me break down actual costs from three projects I have built on Twilio, because abstract per-unit pricing is useless without context.

Project 1: Healthcare appointment reminders. About 8,000 SMS messages per month to US numbers. Two phone numbers. Cost: roughly $68/month ($63 in SMS + $2.30 in number rental + various fees). This is a perfectly reasonable cost for the value it provides.

Project 2: Two-factor authentication for a SaaS app. About 25,000 Verify API calls per month. Cost: roughly $1,250/month at $0.05 per verification. This is where Twilio gets expensive. We evaluated switching to email-only verification or push notifications through Twilio Verify's free channels to bring this down, and ultimately moved low-risk actions to email verification while keeping SMS for high-risk actions, cutting the bill by about 60%.

Project 3: Customer support phone system. About 3,000 inbound call minutes per month, with recording and transcription. Three phone numbers. Cost: roughly $235/month ($25.50 in call charges + $7.50 in recording + $150 in transcription + number rental + platform fees). The transcription cost is the kicker -- at $0.05 per minute, it adds up fast.

The lesson: Twilio's per-unit costs look tiny in isolation. At scale, they compound. Every project needs a cost model before launch, and you should set spending alerts from day one. The pay-as-you-go model is great for prototyping and early-stage products. For production workloads at meaningful volume, negotiate committed-use discounts with Twilio's sales team. I have seen customers get 25-40% off listed rates with annual volume commitments.

Twilio vs. the Alternatives

Pros and Cons

The Pragmatic Bottom Line